This invention relates to new derivatives of 5,5-disubstituted pyrimidine-2,4,6-triones of formula I (below). These compounds show a marked antitumor and antimetastatic activity.
In normal tissue there is an equilibrium between synthesis and degradation. Extracellular matrix is degraded by proteinases which belong to at least three groups of matrix metalloproteinases. These are the collagenases, gelatinases and stromelysins. Normally there are specific inhibitors for these catabolic enzymes such as xcex12 macroglobulines and TIMP (=tissue inhibitor of metalloproteinases (MMP)) so that an excessive degradation of extracellular matrix does not occur. Adamalysins are a related group of proteinases. A prominent member of the adamalysins is TACE (TNF-xcex1-converting enzyme).
At least 17 different and yet highly homologous MMP species have been characterized, including the interstitial fibroblast collagenase (MMP-1, HFC), the neutrophil collagenase (MMP-8, HNC), two gelatinases, stromelysins (such as HSL-1) and HPUMP (for a recent review, see Birkedal-Hansen, H., et al., Critical Rev. Oral Biol. Med. 4 (1993) 197-250). These proteinases share a number of structural and functional features but differ somewhat in their substrate specificity. Only HNC and HFC are capable of cleaving type I, II and III native triple-helical collagens at a single bond with the production of fragments xc2xe and xc2xc of the native chain length. This lowers the collagen melting point and makes them accessible to further attack by other matrix degrading enzymes.
However, the uncontrolled excessive degradation of this matrix is a characteristic of many pathological states such as e.g. in the clinical manifestation of rheumatoid arthritis, osteoarthritis and multiple sclerosis, in the formation of tumor metastases, corneal ulceration, inflammatory diseases and invasion and in diseases of bone and teeth.
The pathogenesis of the foregoing clinical manifestations can be ameliorated by the administration of matrix metalloproteinase inhibitors. A number of such compounds are known (see e.g. the review article of Levy, D. E., Ezrin, A. M., Emerging Drugs 2 (1997) 205-230; Whittaker, M., Brown, P., Curr. Opin. Drug Discovery Dev. 1 (1998) 157-164) or are described in the patent literature, mainly with a hydroxamic acid residue, a thiol or phosphine group as a zinc binding group (see e.g. WO 92/09563 by Glycomed, EP-A 0 497 192 by Hoffinann-La Roche, WO 90/05719 by British Biotechnology, EP-A 0 489 577 by Celltech, EP-A 0 320 118 by Beecham, U.S. Pat. No. 4,595,700 by Searle, WO 97/20824 by Agouron Pharmaceuticals, WO 96/15096 by Bayer Corporation, among others).
Some of these compounds show a high activity as inhibitors of matrix metalloproteinases but their oral availability is very low. Also such compounds often show broad spectrum inhibition of metalloproteinases which may be associated to undesired side-effects and toxicity.
Pyrimidine-2,4,6-trione derivatives have been described in EP 0 869 947 (WO 97/23465) as inhibitors of matrix metalloproteinases. However, there is still a need for new compounds having reduced toxicity and side-effects and a marked inhibitory activity against metalloproteinases, especially as candidates for a chronic treatment against tumor growth and metastasis.
It has now been found that the new pyrimidine-2,4,6-trione derivatives of the present invention have improved activity as matrix metalloproteinase inhibitors as compared to the compounds disclosed in EP 0 869 947.
The present invention is directed to compounds of formula I 
wherein
R1 is selected from the group consisting of a phenyl, phenoxy, phenylthio, phenylsulfinyl, phenylsulfonyl, phenylamino or phenylmethyl residue in which the phenyl moiety optionally may be substituted by one or more halogen atoms, alkoxy, C1-C6 alkyl, cyano, or nitro groups, preferred are substitutions in para and/or meta position by one to two substituents;
R2 is hydrogen;
R3 is selected from the group consisting of hydrogen and lower alkyl, said lower alkyl optionally being interrupted by one or more O, N or S atoms and optionally and independently from each other may be substituted by one or more hydroxyl and oxo groups; and
R4 is selected from the group consisting of lower alkyl that optionally may be interrupted by one or more O, N or S atoms and independently from each other may be substituted by one or more hydroxyl, oxo, aryl, aralkyl, heteroaryl or acyl groups; or alternatively,
R2 and R3 or R3 and R4 together with the nitrogen atom to which they are bound may form a piperazine ring that optionally may be substituted at the second nitrogen atom by an aryl, aralkyl or a heteroaryl group.
The present invention also encompasses pharmaceutically acceptable salts or prodrugs of the compounds of formula I as well as the use of these compounds to produce pharmaceutical compositions.
The aryl group option for R4 and the piperazine ring resulting from the fusion of R3 and R4 consists of a phenyl ring. The heteroaryl group is understood as a cyclic unsaturated ring system consisting of 5 to 7 ring atoms which can be selected from one or more carbon, nitrogen, oxygen or sulfur atoms. Preferred are electron deficient heteroaryl residues such as the nitrogen containing 6-membered rings like pyridines, pyrimidines, pyrazines or 1,3,5-triazines. Most preferred heteroaryl residues are pyrimidinyl or pyrazinyl.
The aryl, alone or as part of an aralkyl group or heteroaryl rings may be substituted by one or more substituents selected from halogen, hydroxy, alkoxy, amino, dialkylamino, cyano, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkinyl, lower acyl, C1-C6 alkylthio C1-C6 alkylsulfonyl, C1-C6 alkylaminocarbonyl, aminocarbonyl, C1-C6 alkylamidosulfonyl, amidosulfonyl, nitro, C1-C6 alkoxycarbonyl, and carboxy. Preferred substitutions are in the para and/or meta positions and preferred substituents are selected from one or two of the above listed substituents.
The aralkyl group is preferably benzyl.
Lower alkyl as used in the definition of R3 and R4 or when used in combinations with other residues denotes C1-C6-alkyl. Preferred lower alkyls are methyl, ethyl, propyl, isopropyl or tert.-butyl.
Preferred R3 and R4 groups are independently selected from the lower alkyl groups that are interrupted by O, N or S, most preferably xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94OHxe2x80x94CH2xe2x80x94CH(OH)xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH3; 2-oxo-[1,3]dioxolan-4-ylmethyl; xe2x80x94CH2xe2x80x94CH(OH)xe2x80x94CH2OH; xe2x80x94CH2xe2x80x94CH(OH)xe2x80x94CH2xe2x80x94Oxe2x80x94CH3 and CH2xe2x80x94CH2 OH. 
Acyl as used in the definition of R4 denotes COxe2x80x94(C1-C6)alkyl; xe2x80x94C(O)xe2x80x94(C1-C6)-alkylen-COOH; xe2x80x94CO-aryl; xe2x80x94CO-aralkyl or xe2x80x94CO-heteroaryl.
Aryl and heteroaryl as used in R4 have the same definitions given above.
Halogen means fluorine, chlorine, bromine and iodine, preferably chlorine or bromine.
If compounds of the formula I contain one or several asymmetric carbon atoms, the optically active compounds of the formula I are also a subject matter of the present invention.
Compounds of the formula I can be synthesized by processes known to those skilled in the art. Preferably compounds of formula I are prepared by reacting a compound of formula II 
wherein R1 is as defined above and T represents a leaving group such as Hal or OSO2R10, Hal is chlorine, bromine or iodine, and R10 is an aryl or a methyl residue,
with a compound of formula III 
wherein R2, R3 and R4 are as defined above.
Compounds of formula I may then optionally be converted into pharmaceutically acceptable salts by conventional means known to one skilled in the art.
Compounds of the formula II can be synthesized by analogy to known literature procedures. For example pyrimidine-2,4,6-triones brominated in the 5-position can be synthesized by reacting the appropriate bromomalonic acid dialkyl esters with urea (e.g. Acta Chim. Acad. Sci. Hung. 107 (2) (1981) 139). The corresponding brominated or chlorinated compounds of the formula II can be obtained by reacting pyrimidine-2,4,6-triones substituted by R1-Phenyl in the 5-position with bromine (analogous to J. Prakt. Chemie 136 (1933) 329 or J. Chem. Soc. 1931, 1870) or sulfuryl chloride (J. Chem. Soc. 1938, 1622) or N-bromo-succinimide or similar brominating agents. Such procedures are also described in EP 0 869 947.
Amines of the formula III are commercially available, are known in the literature, or can be prepared analogously to published procedures. A preferred procedure for the synthesis of monosubstituted alkylpiperazines consists of alkylating mono-benzyl-piperazine with an alkylating agent such as an alkyl halide, e.g. a bromide or a iodide, or a sulfonate ester of an alcohol, e.g. a tolenesulfonate or methylsulfonate ester, in the presence of a base such as sodium hydride or potassium carbonate in an aprotic solvent like dimethylformamide.
Compounds of formula I wherein R4 is acyl can be prepared by acylation of a compound wherein R4 is hydrogen. Such a compound can be obtained by cleavage of a compound of formula I wherein R4 is a nitrogen protecting group, e.g. benzyl.
Pyrimidine-2,4,6-triones of formula II with T representing hydrogen can be prepared according to known methods by reacting malonic acid esters with urea. See for example J. Med. Chem. 10 (1967) 1078; Helvetica Chem. Acta 34 (1959) 459; Pharmacie 38 (1) (1983) 65, or EP 0 869 947. The reactions are usually carried out in alcohols such as methanol, ethanol or butanol in the presence of an appropriate sodium alcoholate at temperatures between 40xc2x0 C. and 100xc2x0 C.
The malonic acid esters which are needed for the preparation of pyrimidine-2,4,6-triones are known from the literature or can be produced according to processes known from the literature. A convenient process for the preparation of malonic acids where R1 has the above mentioned meaning is described in the following scheme: 
Examples for these reactions can be found in Houben-Weyl, Vol. E5/2, J. Org. Chem. 46 (1981) 2999 and Arch. Pharm. 323 (1990) 579.
Compounds of the formula I can contain one or several chiral centers and can then be present in a racemic or in an optically active form. The racemates can be separated according to known methods into the enantiomers. Preferably, diastereomeric salts that can be separated by crystallization are formed from the racemic mixtures by reaction with an optically active acid, such as e.g. D- or L-tartaric acid, mandelic acid, malic acid, lactic acid or camphorsulfonic acid, or with an optically active amine, such as e.g. D- or L-xcex1-phenyl-ethylamine, ephedrine, quinidine or cinchonidine.
Alkaline salts, earth alkaline salts like Ca or Mg salts, ammonium salts, acetates or hydrochlorides are mainly used as pharmaceutically acceptable salts which are produced in the usual manner, e.g. by titrating the compounds with inorganic or organic bases or inorganic acids, such as e.g. sodium hydroxide, potassium hydroxide, aqueous ammonia, C1-C4-alkyl-amines such as e.g. triethylamine or hydrochloric acid. The salts are usually purified by reprecipitation from water/acetone.
The new compounds of formula I and salts thereof according to the invention are useful in the preparation of pharmaceutical compositions that can be administered enterally or parenterally in a liquid or solid form. All typical forms of administration of pharmaceutical compositions are appropriate, such as for example tablets, capsules, coated tablets, syrups, solutions, suspensions, etc. Water which contains additives such as stabilizers, solubilizers and buffers that are usual in injection solutions is preferably used as the injection medium.
Additives such as tartrate and citrate buffer, ethanol, complexing agents (such a ethylenediaminetetra-acetic acid and non-toxic salts thereof), high-molecular polymers (such as liquid polyethylene oxide) may be used to regulate viscosity of pharmaceutical compositions according to the invention. Liquid carrier substances for injection solutions have to be sterile and are preferably dispensed into ampoules. Typical solid carriers useful in the preparation of the pharmaceutical compositions of the invention include starch, lactose, mannitol, methylcellulose, talcum, highly dispersed silicic acids, higher molecular fatty acids (such as stearic acid), gelatins, agar-agar, calcium phosphate, magnesium stearate, animal and vegetable fats, solid high-molecular polymers (such as polyethylene glycols).
Pharmaceutical preparations for oral application may also contain flavorings and sweeteners.
The dosage of the compounds of the invention depends on various factors such as manner of administration, species, age and/or individual state of health. A typical therapeutic amount of a compound of formula I is about 10-1000 mg, preferably 100-500 mg administered daily. This daily amount may be given in one single dose or distributed over several doses.
Prodrugs of the compounds of the invention are these compounds that are converted in vivo to the pharmacological active compound. The most common prodrugs are carboxylic acid esters.